In situ electro-generated Ni(OH)2 synergistic with Cu cathode to promote direct ammonia oxidation to nitrogen

Abstract

To solve the problem of low removal rate and poor N2 selectivity in direct electrochemical ammonia oxidation (EAO), commercial Ni foam and Cu foam were used as anode and cathode of the EAO system, respectively. The coupling effect between the cathode and anode promoted nitrogen cycling during the reaction process, which improved N2 selectivity of the reaction system and promoted it to achieve a high ammonia removal rate. This study showed that the thin Ni(OH)2 with oxygen vacancy formed on the surface of Ni foam anode played an effective role in the dimerization of intermediate products in ammonia oxidation to form N2. This electrochemical system was used to treat real goose wastewater containing 422.5 mg/L NH4+-N and 94.5 mg/L total organic carbon (TOC). After treatment, this electrochemical system achieved good performance with an ammonia removal rate of 87%, N2 selectivity of 77%, and TOC removal rate of 72%. Therefore, this simple and efficient system with Ni foam anode and Cu foam cathode is a promising method for treating ammonia nitrogen wastewater. HIGHLIGHTS The use of commercial electrodes has increased the practicality of this system.; The anode was responsible for the ammonia oxidation.; The cathode was responsible for the reduction of nitrate.; The nitrogen cycle between the electrodes enabled this system to achieve high performance.; The electrochemical system had achieved significant results in practical goose wastewater treatment.;

Keywords

• coupling effect
• direct electrochemical ammonia oxidation
• goose-raising wastewater
• n2 selectivity
• nitrogen cycle